GB2258830A - Screening particulate material - Google Patents

Abstract

A screen deck apparatus (10) has a screen deck (12) that includes a series of flexible, parallel rods (14) and means (18) such as projections 26 on a moving belt 20, for flexing the rods in a direction transverse to their length. When material for screening is deposited on the screen deck, the vibrations set up as a result of transverse flexure of the rods serve to break up any agglomerated particles. The apparatus can be used to screen diamondiferous gravels or kimberlite ore. <IMAGE>

Description

SCREEN DECK APPARATUS AND METHOD OF SCREENING PARTICULATE MATERIAL THIS invention relates to a screen deck apparatus and to a method of screening particulate material.

In the handling of particulate material including agglomerations of individual particles it is often desirable to disagglomerate the particles to facilitate later operations on the individual particles. One example where this practice would be desirable is in particle sorting, where desired particles may be shielded in agglomerations of other undesired particles and where the efficiency of the subsequent sort is dependent to a greater or lesser degree on the exposure of discrete particles.

According to a first aspect of the invention there is provided a screen deck apparatus comprising a screen deck that includes a series of flexible, parallel rods, and means for flexing the rods in a direction transverse to their length.

In the preferred version of the invention, the rod flexing means operates to flex the rods individually in sequence. Typically, the flexing means includes one or more contact members for contacting the rods individually in sequence in a manner to cause the rods to flex transversely.

The apparatus may also include means for causing relative movement to take place, in a direction transverse to the rod lengths, between the screen deck and the contact member or members.

In the preferred embodiment, the flexing means comprises a belt, one or more projecting formations on the belt and means for moving the belt relative to the screen deck so that the projecting formation or formations contact the individual rods of the screen deck in sequence and cause them to flex transversely to their length. In this embodiment, the screen deck comprises a first stringer to which one end of each rod is connected and a second stringer which is spaced from and parallel to the first stringer and which is formed with holes through which opposite end regions of the rod project loosely.In this situation, the projecting formations on the belt act on the opposite end regions of the rods. According to a second aspect of the invention there is provided a method of screening particulate material, the method comprising the steps of depositing the material on the surface of a screen deck of an apparatus as summarised above, and flexing the rods of the screen deck in a direction transverse to their length so as to cause disagglomeration of the agglomerations in the particulate material.

In one application, the apparatus and method of the invention are used to screen diamondiferous gravels or kimberlite ore.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a plan view of a screen deck apparatus of the invention; and Figure 2 shows a side view of the apparatus seen in Figure 1.

The illustrated screen deck apparatus 10 incorporates a screen deck 12 composed of a series of closely spaced parallel rods 14. The rods 14 are made of an inherently resilient material, such as plastics or metal, the exact choice of material being dependent on the nature of the material which is to be screened by the screen deck 12. The rods 14 are quite slender and therefore have considerable flexibility in a direction transverse to their lengths.

One end of each rod 14 is fixed to a transverse stringer 16. The opposite ends of the rods 14 pass through oversize holes 15 in a further stringer 17, so that the extremities 19 of the rods project past the stringer 17 as illustrated.

The screen deck apparatus 10 also includes a flexing device 18. In this embodiment, the flexing device 18 includes an endless belt 20 passing around a driven pulley 22 and an idling pulley 24. The belt 20 has a series of spaced projections, in the form of rubber knuckles 26, projecting from its surface as illustrated. The belt is arranged to move over the extremities 19 of the rods 14, in a direction transverse to the lengths of the rods.

In use of the apparatus 10, particulate material which is to be screened is deposited onto the upper surface of the screen deck 12, possibly along a chute fed by a hopper or the like. At the same time, the belt 20 is driven to cause the rubber knuckles 26 to brush over the extremities 19 of the rods 14 of the screen deck. As the extremity of each rod 14 is contacted forcibly by a rubber knuckle, it is caused to flex resiliently in a direction transverse to its length, as exemplified by the rods 14A in the Figures. It will be appreciated that this flexure is permitted by the loose passage of the rods through the oversize holes 15 in the stringer 17.

As the relevant knuckle 26 moves on and breaks contact with the rod extremity, the rod springs back to its original shape, but it will vibrate to some degree before settling in the original, unflexed state.

Small, discrete particles having a dimension less than the initial rod spacing will of course be able to drop through the screen deck immediately. Larger agglomerations of particles that are unable to pass through the screen deck will reside on the upper surface thereof. The vibrations set up in the individual rods by passage of the rubber knuckles 26 over the rod extremities will tend to break the agglomerations up into individual, discrete particles which will, if small enough, then be able to drop through the screen deck.

It is therefore anticipated that the screen deck apparatus described above will be useful in screening particulate masses, either alone or in combination with other screening or sizing equipment. At the same time, it is believed that the apparatus will function efficiently to exclude particle agglomerations from the screened material. Naturally, the initial spacing of the rods 14 will be chosen in accordance with the desired particle sizes that are to be achieved in a particular application. In one application, a screen deck apparatus of the kind described above can be used to screen and disagglomerate diamondiferous gravels recovered from alluvial deposits, or kimberlite ore recovered from underground mining operations and subsequently crushed. In each of these cases, the intention will be to remove oversize material and also to disagglomerate the diamond particles from the associated non-diamond material.

It will readily be recognised that the individual flexing of the rods 14, leading to vibrations thereof, is of major benefit when compared to a conventional vibratory screen. In a vibratory screen, the entire screen is vibrated. This may well fail to break up individual agglomerations of particles, which may tend merely to be shaken back and forth on the surface of the vibrating screen. With individually vibrating rods in localised zones of the screen deck, as proposed above, it is believed that the potential for disagglomeration will be enhanced.

Claims (11)

1.

A screen deck apparatus comprising a screen deck that includes a series of flexible, parallel rods, and means for flexing the rods in a direction transverse to their length.

2.

A screen deck apparatus according to claim 1 wherein the rod flexing means operates to flex the rods individually in sequence.

3.

A screen deck apparatus according to claim 2 wherein the flexing means includes one or more contact members for contacting the rods individually in sequence in a manner to cause the rods to flex transversely.

4.

A screen deck apparatus according to claim 3 wherein the apparatus includes means for causing relative movement to take place, in a direction transverse to the rod lengths, between the screen deck and the contact member or members.

5.

A screen deck apparatus according to claim 4 wherein the flexing means comprises a belt, one or more projecting formations on the belt and means for moving the belt relative to the screen deck so that the projecting formation or formations contact the individual rods of the screen deck in sequence and cause them to flex transversely to their length.

6.

A screen deck apparatus according to claim 5 wherein the screen deck comprises a first stringer to which one end of each rod is connected and a second stringer which is spaced from and parallel to the first stringer and which is formed with holes through which opposite end regions of the rod project loosely.

7.

A screen deck apparatus according to claim 6 wherein the projecting formations on the belt act on the opposite end regions of the rods.

8.

A method of screening particulate material, the method comprising the steps of depositing the material on the surface of a screen deck of an apparatus according to any one of the preceding claims, and flexing the rods of the screen deck in a direction transverse to their length so as to cause disagglomeration of the agglomerations in the particulate material.

9.

A screen deck apparatus according to any one of claims 1 to 7 when used to screen diamondiferous gravels or kimberlite ore.

10.

A screen deck apparatus substantially as herein described with reference to the accompanying drawings.

11.

A screening method substantially as herein described with reference to the accompanying drawings.